This invention relates to interleaved carbonless forms comprising pressure-sensitive coated-back sheets and coated front receiver sheets which can be printed xerographically and which resist smudging caused by non-specific development of the coated front receiver sheets.
Carbonless copy paper comprises to or more juxtaposed sheets. The back surfaces of the sheets have a coating containing a color-forming material often referred to as a "coated back" or "CB" coating. The coating consists of a continuous matrix or microcapsules containing a pale or colorless color-forming material which is designed to rupture and release the color-former when a threshold pressure is applied to the front or opposite side of the sheet. The front surfaces of the receiver sheets, which in use are placed in contact with the coated back surfaces of the overlaid sheets, are coated with a composition containing a developer component reactive with the color-forming material in the CB sheets which are capable of changing it to colored condition. These sheets are referred to as "coated front" or "CF" sheets. The multi-layered set of carbonless forms will consist of a top sheet having only a CB coating, a bottom sheet having only a CF coating and one or more intervening sheets having both CB and CF coatings. Typically, the forms also include printed indicia on the top surface of at least the top sheet and one or more of the underlying sheets, and blank spaces where information is filled in by writing or typing. Upon the application of pressure to the top sheet, the CB coatings are ruptured thereby releasing the color-forming material imagewise to contact, react with and form a visible color in the developer coating on the CF sheets. A visible color image is produced in areas corresponding to the locations when pressure has been applied to release the color-forming material. Pressure applied to the top sheet causes a corresponding mark on the front of each sheet in the manifold set. Thus, multiple "carbon" copies can be made at once.
These carbonless forms are widely used in business, particularly in retailing. One drawback to these sheets is that the application of non-specific pressure, such as a heavy object being placed on the sheets, can rupture the CB coating, causing smudging or non-specific development of the underlying CF sheets. Non-specific development can occur when CB forms are xerographically reproduced due in part to the pressure of the feeder and/or fuser rolls in the copier. The same problem can occur when carbonless sheets are run through laser printers. Carbonless paper is needed which resists non-specific development but forms clear copies when specific pressure is applied.